This invention relates to a combined magnetic tape head for use in recording equipment, and more particularly to a combined magnetic tape head for use in cassette type or cartridge type equipment. This equipment genrally comprises a recording head covered by a shield case, a so-called playback head covered by a shield case and a flat chip for providing a desired contact condition between a magnetic recording tape and the recording and playback heads.
Generally, tape equipment requires at least two separate heads, that is, an erase head which cleans a magnetic recording tape of previous recordings and noise, and a combined recording and playback head. As shown in FIG. 1, the combined recording/playback head comprises a recording head 2 including a ringshaped core having a gap 6, coils wound around the core (not shown), a shield case 4 and an anti-magnetic frame 14, and a playback head 3 includes a ring-shaped core having a gap 6', coils wound around the core (not shown), a shield case 5 and an anti-magnetic frame 14'. The recording and the playback heads are combined into a unitary element by means of a suitable means such as a tightening band 7 and/or an adhesive agent.
The recording tape travelling operation in conventional cassette or cartridge equipments will now be described with reference to FIG. 2 in the attached drawings. FIG. 2 is a schematic side view illustrating the relationship between a conventional combined recording/playback head and a magnetic recording tape 8. The recording tape 8 travels over a recording head 2 and a playback head 3 under suitable pressure caused by biasing the tape 8 toward the heads 2 and 3 by means of a common flexible pad 9. Force is applied to the tape 8 in the direction of the vertical arrow in FIG. 2. The common flexible pad 9 is normally contained and fixed in a cassette type recording tape or a cartridge type recording tape. More specifically, the tape 8 travels over the respective arcuate front surfaces of heads 2 and 3 in a condition such that the common pad 9 biases the tape 8 toward a V-shaped groove defined by the arcuate front surfaces of heads 2 and 3 which are provided adjacently to each other. It is therefore possible to obtain the desired contact pressure condition between the tape 8 and the surfaces, that is, to obtain a preferable wrap angle as shown in FIG. 2.
It should be noted that, the arcuate front surfaces thereof are represented by circular arcs having the same radiuses R, respectively, and the wrap angle in each head is representative of a central angle corresponding to an arcuate front surface of the head which the tape contacts. In this construction, however, it is difficult to maintain the desired contact of the tape 8 to arcuate front surfaces of heads due to lack of uniformity in the biasing force.
In order to eliminate the above drawbacks, according to experiments performed by the present inventor, it has been established that a flat chip 10 made of non-magnetic material may be provided over the above mentioned V-shaped groove in a bridge like manner as shown in FIG. 3. With such an assembled combined head, a distance "d" is established from a phantom tangent plane including the top end portions in the arcuate front surfaces of the heads, to the top surface of the chip 10. This distance "d", that is, the distance between a tangent extending from the tops of the gaps 6 and 6' to the front surface of flat chip 10, is selected to be within the range of about 0.01 to 0.3 mm when the travelling tape 8 is biased toward the heads by the pad 9. Due to this construction it is possible to obtain a more preferable wrap angle than the conventional combined head shown in FIG. 2. This prior art has been disclosed in a published unexamined Japanese patent application No. 53--111710 which was laid-open for public inspection on Sept. 29, 1978.
With the combined recording/playback head as described above, however, the flat chip 10 has to be attached to the arcuate front head surfaces by an adhesive agent. The flat chip 10 to be attached must be maintained by means of suitable jigs in a fixed condition that satisfies the above mentioned condition until the chip 10 is fixedly positioned by curing of the adhesive agent. This is disadvantageous in that the head manufacturing step requires jigs and therefore the manufacturing efficiency is decreased. Thus, such a prior art combined head is not suitable to mass-production.
Also, the chip 10 may eventually be displaced by constant running of the tape 8, or as a result of rough handling of the recorder, for example by careless or negligent cleaning of the heads.